A turbine engine comprises a gas generator which comprises, in particular, one or more compressors, for example low-pressure and high-pressure compressors, arranged upstream of a combustion chamber.
By convention, in the present application, the terms “upstream” and “downstream” are defined with respect to the gas flow direction in the turbine engine. Similarly, by convention in the present application, the terms “inner” and “outer” are defined radially with respect to the longitudinal axis of the turbine engine, which is in particular the axis of rotation of the rotors of the compressors.
Traditionally, the combustion chamber is annular with an axis C of revolution and is placed in an annular enclosure which is radially delimited by an outer annular casing and an inner annular casing. The combustion chamber is delimited by coaxial inner and outer annular walls which are joined upstream by a substantially transverse, also annular, bottom of the chamber.
The combustion chamber is in particular supplied with compressed air coming, for example, from a high-pressure compressor arranged upstream of the combustion chamber, in particular via an annular diffuser, and with fuel via injection devices which are angularly distributed around the axis C. The combustion of the air/fuel mixture is initiated by an ignition device and in particular generates thermal radiation from downstream to upstream towards the bottom of the chamber, the bottom of the chamber thus being subjected to high temperatures. In order to protect the bottom of the chamber, at least one annular deflector (also called a heat shield) is placed in the combustion chamber facing the bottom in a substantially parallel manner, and at a short distance from this. The deflector is generally divided into sectors and formed of a plurality of deflector sectors which are angularly distributed around the axis C.
The deflector sectors are cooled by the impact of air jets which also come from the high-pressure compressor and enter the combustion chamber through cooling orifices formed in the bottom of the chamber.
In this way, the cooling air of the deflector sectors, flowing from upstream to downstream, passes through the bottom of the chamber through the cooling orifices and then impacts the deflector sectors. The air is then guided radially towards the interior and exterior of the chamber in order to introduce, on each of the inner and outer walls, a film of cooling air which flows from upstream to downstream.
Even though this architecture makes it possible to slightly cool the inner and outer walls on an upstream portion of the chamber, it nevertheless poses some difficulties, in particular when the turbine engine is operating at an idle speed.
In fact, in particular at an idle speed, these films of cooling air trap fuel and, in other words, a quantity of fuel (generally hydrocarbons) is unburnt, which is disadvantageous for combustion efficiency.
The prior art included published patent applications EP-A1-2012061, EP-A1-2728263, US-A1-2016/054003, EP-A2-1271059, EP-A2-0724119, and WO-A1-2014/052965, each of which is hereby incorporated by reference.